High accuracy fluid pumps having flow rates on the order of microliters per minute (.mu.l/min) which can be fabricated by micromachining techniques have gained interest in the last few years. Applications for micropumps include small dosage in-vivo drug release, on-chip cooling systems, integrated chemical analysis systems, chemical processing, and mixing.
Prior art microfabricated pumps have included flexible diaphragm valves working peristaltically and flexible diaphragm valved electrothermopneumatic liquid pumps. The flow of liquid in such pumps is pulsating. This type of pump also suffers from valve leakage. There is a need for a micropump which has no moving parts in which the fluid flow can be electronically controlled.
This invention uses longitudinal acoustic waves which travel along a microchannel and cause the liquid to flow in the direction of the acoustic wave as a result of pressure gradients caused by attenuation of the sound waves in the fluid or variations in radiation pressure in the channel or by both mechanisms.